The present invention relates to the formation of a cosmetic and chemically stable hydrogen peroxide-containing dental gel having an acid pH of about 3-6 comprising a compatible system of specified amounts of specific dental components, desirably prepared by a specific order of addition of the various ingredients.
Until now it has been difficult to formulate a cosmetic and chemically stable hydrogen peroxide gel with appropriate thickening/gelling agents, humectant, surfactants and flavor for oral application. However, after extensive experimentation on various mixtures of components in the hydrogen-peroxide dental gel product, a compatible system of water, a combination of hydrophilic and hydrophobic fumed silica as gelling agent, polyethylene glycol humectant, nonionic surfactant, sweetening agent, sodium benzoate, and flavor has been discovered. It has also been found that the order of addition of these ingredients is important in the formation of a stable gel.
Accordingly, it has been discovered that by using a specific sequential step process, stable formulations of a hydrogen peroxide dental gel containing a combination of hydrophilic and hydrophobic fumed silica as gelling agent, a polyethylene glycol hymectant, a nonionic surfactant, sweetening agent, sodium benzoate, and flavor can be made. The stable hydrogen peroxide gel is prepared by homogenizing the fumed silicas in the polyethylene glycol and water phases and the sequential addition of the premixed homogenized hydrophobic fumed silica in the polyethylene glycol (Phase A) to the premixed homogenized hydrophilic fumed silica in water containing hydrogen peroxide (Phase B) and mixing for about 30 minutes while maintaining the temperature at room temperature, adding the predissolved sodium saccharin and sodium benzoate in water (Phase C) with mixing which effects immediate gellation, adding the presolubilized flavor in the nonionic surfactant and water (Phase D) and mixing for about 5-10 minutes until a clear, homogeneous rigid stable dental gel is obtained.
The finished oral product is a stable rigid gel having improved chemical and cosmetic stability and improved taste.
It has long been recognized in the art that hydrogen peroxide and other peroxygen-containing agents are effective in curative and/or prophylactic treatments with respect to caries, dental plaque, gingivitis, periodontitis, mouth odor, tooth stains, recurrent aphthous ulcers, denture irritations, orthodontic appliance lesions, postextraction and postperiodontal surgery, traumatic oral lesions and mucosal infections, herpetic stomatitis and the like. Peroxide-containing agents in the oral cavity exert a chemomethanical action generating thousands of tiny oxygen bubbles produced by interaction with tissue and salivary enzymes. Peroxide mouthrinses and other oral preparations prevent colonization and multiplication of anaerobic bacteria known to be associated with periodontal disease. Peroxygen-containing gels or pastes are indicated and/or desirable where it is required to selectively treat areas for more than a few seconds, such gels and pastes tending to remain at the site of application for a time sufficient for the peroxide to manifest its maximum effectiveness.
It is also known that most peroxy compounds such as hydrogen peroxide in oral compositions tend to be unstable in storage due to incompatability with and/or interaction with other common ingredients in the composition, and lose the capacity to release active or nascent oxygen over relatively short periods of time. This adversely affects both the chemical stability of the composition as well as the cosmetic stability of the final product, particularly in the gel product containing hydrogen peroxide.
The prior art has attempted to solve said problems by using a variety of stabilizers for dental compositions in assorted forms such as tablets, chewing gum, mouthwashes, toothpastes, or powder containing a hydrogen peroxide as shown in U.S. Pat. No. 4,226,851 wherein is disclosed an aqueous mouthwash containing hydrogen peroxide, flavor, zinc chloride and water soluble Vitamin E which stabilizes the hydrogen peroxide in the mouthwash. U.S. Pat. No. 4,302,441 discloses solid oral products (tablets and chewing gum) containing urea hydrogen peroxide in gum bases such as jelutong, rubber latex, vinylite resins, etc., and in methyl, ethyl and sodium carboxymethyl cellulose carriers, free of glycerol, also containing sweeteners such as sodium saccharinate, xylitol, sorbitol, and mannitol and flavors. U.S. Pat. No. 4,476,108 discloses an admixture of peroxidase, a peroxide and a donor molecule such as phenylethylamine tyrosine, tryptophan, benzoic acid, salicylic acid, hydroquinone, dehydrophenyl-alanine, vanillan and para-aminobenzoic acid, in a carrier such as water (mouthwash) or in the form of a paste, gel or powder. U.S. Pat. No. 4,431,631 discloses an aqueous oral solution containing hydrogen peroxide, glycerin and/or sorbitol humectant, 0.5-3% pluronic-type surfactant, polyoxyethylenated sorbitol monofatty acid ester surfactant, sweetener and flavor.
The prior art also discloses dental compositions containing a hydrogen peroxide and an additional component to effect stabilization, such as ascorbic acid in U.S. Pat. No. 3,886,265, wherein is disclosed tablets, lozenges, chewing gum or an aerosol or spray form containing a peroxide such as hydrogen peroxide and an ene-diol compound such as ascorbic acid, effective against bad breath.
U.S. Pat. No. 4,521,403 discloses a method of controlling and treating periodontal diseases by washing the teeth with an aqueous or aqueous alcoholic solution of a hydrogen peroxide and a povidone-iodine complex (complex of iodine with 1vinyl-2-pyrrolidone polymers). These two ingredients are mixed only prior to use. U.S. Pat. No. 4,592,487 discloses an antiplaque dentifrice in the form of a toothpaste or gel containing the two components, a peroxide and povidone-iodone complex, each separately mixed with conventional dentifrice components, and kept separated until admixed and dispensed from a special dual compartment container/mixer/dispenser device. U.S. Pat. No. 4,592,488 discloses an oral mouthwash containing an iodophor or quaternary ammonium compound and a peroxy compound such as hydrogen peroxide in the form of an aqueous or aqueous alcoholic solution prior to combining the two components into an oral mouthwash. U.S. Pat. No. 4,592,489 discloses a two-part container for dispensing an oral mouth wash containing the povidone-iodine complex solution separate from the hydrogen peroxide solution and mixing prior to dispensing.
Dental compositions containing other oxidizing agents in lieu of the hydrogen peroxide are also disclosed in the prior art. U.S. Pat. No. 4,405,599 discloses toothpaste containing an oxidizing agent such as carbamide peroxide (urea peroxide) which dissociates into urea and hydrogen peroxide in the oral cavity, in a paste carrier comprising an anionic detergent, sorbitol and glycerin humectant and a thickening agent such as gum tragacanth, sodium alginate or sodium carboxymethyl cellulose. U.S. Pat. No. 4,405,599 discloses toothpaste containing calcium peroxide and sodium perborate oxidizing agents; dicalcium phosphate, calcium carbonate and magnesium carbonate cleaning agents; sorbitol humectant; cornstarch and cellulose gum thickening agents, and an anionic detergent.
However, none of the aforesaid patents disclose the preparation of hydrogen peroxide gels containing the essential specific components of a polyethylene glycol humectant, a nonionic surfactant, flavor, sodium saccharin, sodium benzoate and a combination of hydrophilic and hydrophobic fumed silica gelling/thickening agent in the formation of a stable dental gel.
The prior art also discloses processes of preparing peroxide gels as shown in U.S. Pat. No. 3,657,413 and the article by Assasy et al, "Stability of Hydrogen Peroxide in Certain Pharmaceutical Gels" Cosmetics and Toiletries 54-56, 91, September 1976. The patent discloses a clear gel comprising urea peroxide, glycerol, a carboxypolymethylene polymer and flavor; prepared by dispersing the polymer into the glycerol with high speed stirring at reduced pressure and then dissolving the urea peroxide and other ingredients in the thickened polymer/glycerol solution yielding a viscous gel. The article discloses methyl cellulose gels for treating surface cuts, bleaching hair and for deodorant purposes containing 0.1% oxine as stabilizer for the hydrogen peroxide; prepared by dispersing the methyl cellulose in water using an electric stirrer and then neutralizing the triethanolamine to yield a gel; or dispersing in hot water until well hydrated, refrigerating until solidified and stirring until a gel is obtained, adding the stabilizer oxine to the gel, followed by the addition of the hydrogen peroxide. Other stabilizers which are not as effective as oxine include hexamine, benzoic acid or urea.
Hydrogen peroxide gels containing polyoxyethylene polyoxypropylene block copolymers as the gelling/thickening agent is disclosed in U.S. Pat. No. 3,639,574 which discloses a stable hydrogen peroxide gel for use in hair bleaching and treating surface cuts, using polyoxyethylene polyoxypropylene block copolymers as gelling agents in amounts of 22-79% of the total compositions, which may be prepared by dissolving the copolymers in water cooled to a temperature of 35.degree.-50.degree. F. and slowly adding the hydrogen peroxide to the cool polymer solution, allowing the solution to warm up to room temperature which forms a clear gel. This method may be varied by first adding the H.sub.2 O.sub.2 to cold water and then adding the copolymer to the cold aqueous solution and mixing until completely dissolved, followed by standing at room temperature until it gels. This in not a dental gel, does not contain the polyethylene glycol humectant, sodium saccharine sweetener, or flavor which are essential ingredients in the dental gel.
Denture cleansers containing 0.5-1.0% CAB-O-Sil, a colloidal, submicroscopic, pyrogenic silica, to maintain a mixture of solid ingredients in a free-flowing state and to prevent lumping is disclosed in U.S. Pat. No. 3,372,125.
U.S. Pat. No. 4,223,003 disclosed toothpaste and powder dentifrices containing a dye, a high foaming surfactant (anionic) to produce colored foam when brushing the teeth, a peroxide-containing compound such as magnesium peroxide, and conventional dental constituents which include carboxymethyl cellulose thickeners, pyrogenic silica, humectants, polishing agnets, flavors, fluorides, etc.
U.S. Pat. No. 4,537,765 discloses a toothpaste having a pH of 9.2-10.5 containing a peroxydiphosphate salt, a polyethylene glycol humectant, a thickener such as colloidal silica, carboxyvinyl polymer, cellulose gums, or hectorite, a polishing agent such as silica or hydrated alumina and anionic or nonionic surfactants such as Pluronic F108.
However, the prior art does not disclose a cosmetic and chemically stable aqueous hydrogen peroxide dental gel having a pH of 3-6 containing as the essential ingredients a combination of hydrophilic and hydrophobic fumed silica gelling agent, a polyethylene glycol humectant, a nonionic surfactant, sweetening agent, sodium benzoate, and flavor prepared by a novel process utilizing a specific sequence of steps, which comprises the sequential addition with mixing of Phase A, a premixed homogenized hydrophobic fumed silica in polyethylene glycol; to Phase B, of premixed homogenized hydrophilic fumed silica in water containing hydrogen peroxide, and mixing for about 30 minutes at room temperature; adding Phase C, predissolved sodium saccharin and sodium benzoate in water to Phase AB to effect gelation; adding Phase D, pre-solubilized flavor in the nonionic surfactant and water to Phase ABC and mixing for about 5-10 minutes until clear, and homogeneous rigid gel is obtained.